Cqi feedback structure

ABSTRACT

Embodiments of the present disclosure provide a reporting allocation unit, an indicator interpretation unit and methods of operating a reporting allocation unit and an indicator interpretation unit. In one embodiment, the reporting allocation unit includes an indicator configuration module configured to provide reporting interval and offset values of corresponding rank and channel quality indicators for user equipment. The reporting allocation unit also includes a sending module configured to transmit the reporting interval and offset values to the user equipment.

CROSS-REFERENCE TO PROVISIONAL APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/038,869, filed by Eko N. Onggosanusi and Runhua Chen on Mar. 24,2008, entitled “CQI Reporting Configuration”, commonly assigned withthis application and incorporated herein by reference.

This application also claims the benefit of U.S. Provisional ApplicationSer. No. 61/041,779, filed by Eko N. Onggosanusi and Runhua Chen on Apr.2, 2008, entitled “CQI Reporting Configuration”, commonly assigned withthis application and incorporated herein by reference.

This application additionally claims the benefit of U.S. ProvisionalApplication Ser. No. 61/043,272, filed by Eko N. Onggosanusi and RunhuaChen on Apr. 8, 2008, entitled “CQI Feedback Structure”, commonlyassigned with this application and incorporated herein by reference.

This application further claims the benefit of U.S. ProvisionalApplication Ser. No. 61/044,708, filed by Eko N. Onggosanusi and RunhuaChen on Apr. 14, 2008, entitled “CQI Feedback Structure”, commonlyassigned with this application and incorporated herein by reference.

This application yet further claims the benefit of U.S. ProvisionalApplication Ser. No. 61/052,544, filed by Eko N. Onggosanusi and RunhuaChen on May 12, 2008, entitled “CQI Feedback Structure”, commonlyassigned with this application and incorporated herein by reference.

This application still further claims the benefit of U.S. ProvisionalApplication Ser. No. 61/077,761, filed by Eko N. Onggosanusi and RunhuaChen on Jul. 2, 2008, entitled “CQI Feedback Structure”, commonlyassigned with this application and incorporated herein by reference.

TECHNICAL FIELD

The present disclosure is directed, in general, to a communicationsystem and, more specifically, to a reporting allocation unit, anindicator interpretation unit and methods of operating a reportingallocation unit and an indicator interpretation unit.

BACKGROUND

A key principle in orthogonal frequency division multiple access (OFDMA)communication systems is that the total operating bandwidth is dividedinto non-overlapping sub-bands, also called resource blocks (RBIs),where transmissions for user equipment (UE) occur in an orthogonal(i.e., not mutually interfering) manner. Each RE can potentially carrydata to a different UE. More typically, each UE having a sufficientlyhigh signal-to-interference and noise ratio (SINR) will use awell-chosen set of RBs, so that the spectral efficiency of thetransmission is maximized according to the operating principle of ascheduler.

By scheduling each UE on RBs where it has high SINR, the data ratetransmitted to each UE, and therefore the overall system throughput, canbe optimized according to the scheduling principle. To enable moreoptimum frequency domain scheduling of UEs in the RBs of the operatingbandwidth, each UE feeds back a channel quality indicator (CQI) it mightpotentially experience for each RB or each combination of RBs to itsserving base station (Node B). Additionally, a transmission rankindicator (RI) that determines the number of data layers multiplexed inthe spatial domain is also fed back. Improvements in the selection andfeed back of rank and channel quality indicators would prove beneficialin the art.

SUMMARY

Embodiments of the present disclosure provide a reporting allocationunit, an indicator interpretation unit and methods of operating areporting allocation unit and an indicator interpretation unit. In oneembodiment, the reporting allocation unit includes an indicatorconfiguration module configured to provide reporting interval and offsetvalues of corresponding rank and channel quality indicators for userequipment. The reporting allocation unit also includes a sending moduleconfigured to transmit the reporting interval and offset values to theuser equipment.

In another embodiment, the indicator interpretation unit includes areceive module configured to receive reporting interval and offsetvalues for corresponding rank and channel quality indicators from a basestation. The indicator interpretation unit also includes a reportingconfiguration module configured to provide the reporting interval andoffset values for feeding back the corresponding rank and channelquality indicators to the base station.

In another aspect, the method of operating the reporting allocation unitincludes providing reporting interval and offset values of correspondingrank and channel quality indicators for user equipment and transmittingthe reporting interval and offset values to the user equipment.

In yet another aspect, the method of operating the indicatorinterpretation unit includes receiving reporting interval and offsetvalues for corresponding rank and channel quality indicators from a basestation and providing the reporting interval and offset values forfeeding back the corresponding rank and channel quality indicators tothe base station.

The foregoing has outlined preferred and alternative features of thepresent disclosure so that those skilled in the art may betterunderstand the detailed description of the disclosure that follows.Additional features of the disclosure will be described hereinafter thatform the subject of the claims of the disclosure. Those skilled in theart will appreciate that they can readily use the disclosed conceptionand specific embodiment as a basis for designing or modifying otherstructures for carrying out the same purposes of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A and 1B illustrate diagrams of a downlink portion and an uplinkportion of a communications system as provided by one embodiment of thedisclosure;

FIGS. 2A and 2B illustrate diagrams of reporting structures as may beemployed in the downlink and uplink portions of FIGS. 1A and 1B.

FIG. 3 illustrates a flow diagram of an embodiment of a method ofoperating a reporting allocation unit carried out according to theprinciples of the present disclosure; and

FIG. 4 illustrates a flow diagram of an embodiment of a method ofoperating an indicator reception unit carried out according to theprinciples of the present disclosure.

DETAILED DESCRIPTION

To support MIMO transmission, the following reports are supported forE-UTRA (Evolved UMTS Terrestrial Radio Access) Long Term Evolution(LTE). A rank indicator (RI) report that enables a Node E to adapt atransmission rank (the number of spatial streams or layers for spatialmultiplexing) in spatial multiplexing. A channel quality indicator (CQI)report for closed-loop spatial multiplexing, wherein one CQI is reportedfor one code word (rank-1) transmission and two CQIs, each correspondingto one code word, are reported for a two code word (i.e., rank greaterthan one) transmission. For open-loop spatial multiplexing, only one CQIis reported. A precoding matrix indicator (PMI) report that is only usedfor closed-loop spatial multiplexing. Embodiments of the presentdisclosure provide reporting structures for these reports.

FIGS. 1A and 1B illustrate diagrams of a downlink portion 100 and anuplink portion 150 of a communications system as provided by oneembodiment of the disclosure. In the illustrated embodiment, thecommunications system is an orthogonal frequency division multipleaccess (OFDMA) system, which provides a total operating bandwidthdivided into non-overlapping RBs. The RBs provide transmissions fordifferent UEs that occur in an orthogonal or substantially independentmanner wherein each RB can potentially carry data to a different UE.

FIG. 1A illustrates a system diagram of the downlink portion 100, whichcorresponds to a base station transmitter (Node B) and includes atransmit portion 105, a feedback decoder 110 and a reporting allocationunit 115. The transmit portion 105 includes a modulation and codingscheme (MCS) module 106, a precoder module 107 and an OFDM module 108having multiple OFDM modulators that feed corresponding transmitantennas.

The feedback decoder 110 includes a receive module 111 and a decodemodule 112. The receive module 111 receives transmission rank indicator(RI) and channel quality indicator (OQI) information as well asprecoding matrix indicator (PMI) selections that have been fed back fromuser equipment. The decoding module 112 extracts the RI, CQI and PMIselections wherein they are provided to the transmit portion 105 toallow efficient data transmission over multiple antennas through acommunication network 120.

The MCS module 106 employs the RI selection to map input data toindicated spatial streams (1-R). A scheduling function (not specificallyshown) employs the CQI selection to assign RBs to each of the userequipment. The precoder module 107 then maps the spatial streamslinearly into output data streams for transmission by the OFDM module108 over the communication network 120.

The reporting allocation unit 115 includes an indicator configurationmodule 116 and a sending module 117. The indicator configuration module116 is configured to provide reporting interval and offset values ofcorresponding rank and channel quality indicators for user equipment.The sending module 117 is configured to transmit the reporting intervaland offset values to the user equipment. The reporting interval andoffset values are sent by a radio resource control (RRC) channel throughthe communication network 120 to inform the UE of the structure to beused to feed back RI, CQI and PMI selections to the feedback decoder110. The reporting interval and offset values are also provided to thefeedback decoder 110 for decoding purposes.

FIG. 13 illustrates a system diagram of the uplink portion 150 asprovided by one embodiment of the disclosure. In the illustratedembodiment, the uplink portion 150 corresponds to a UE receiver andincludes a receive portion 155, a feedback generator 165 and anindicator interpretation unit 170. The receive portion 155 includes achannel estimation unit 156, a link adaptation unit 157 and a MIMOdemodulation unit 161.

The receive portion 155 is primarily employed to receive data signalsfrom a transmission corresponding to RI, CQI and PMI information whereinthe MIMO demodulation unit 161 ultimately provides data output. Thechannel estimation unit 156 employs previously transmitted channelestimation signals to provide the channel estimates need by the receiveportion 155. The link adaptation unit 157 includes an RI selector 158, aCQI selector 159 and a PMI selector 160. The rank selector 158 providesa transmission rank selection. The CQI selector 159 provides a channelquality based on channel estimation and the precoding selector 160provides a precoding matrix selection.

The feedback generator 165 includes an encode module 166 and a transmitmodule 167. The encode module 166 accepts the rank, channel quality andprecoding matrix selections from the link adaptation unit 157 andencodes them for feeding back based on a reporting structure provided bythe indicator interpretation unit 170. The transmit module 167 thenfeeds back the reporting structure to the downlink portion 100.

The indicator interpretation unit 170 includes a receive module 171 anda reporting configuration module 172. The receive module 171 isconfigured to receive reporting interval and offset values forcorresponding rank and channel quality indicators from the downlinkportion 100. The reporting configuration module 172 is configured toprovide the reporting interval and offset values to the feed backgenerator 165 for feeding back the corresponding rank and channelquality indicators to the downlink portion 100.

FIGS. 2A and 2B illustrate diagrams of reporting structures, generallydesignated 200, 250, as may be employed in the downlink and uplinkportions 100, 150 of FIGS. 1A and 1B.

For PUCCH-based periodic reporting, RI may be seen to be reportedseparately from CQI/PMI. That is, RI and wideband CQI/PMI are notreported in the same subframe (i.e., reporting instance). The reportinginterval of the RI report is an integer multiple (M) of the widebandCQI/PMI reporting interval. The same or different offsets between the RIand wideband CQI/PMI reporting instances may be configured. Here, an RIreporting offset ν_(RI) may be defined either as an absolute offset orrelative to a CQI/PMI reporting offset ν_(CQI). Both the reportinginterval and offset are configured by higher layers. In the case of acollision of RI and wideband CQI/PMI, the wideband CQI/PMI is dropped.

Denote the reporting interval of RI and CQI/PMI as ρ_(RI) and ρ_(CQI),respectively. Therefore, ρ_(RI)=M×ρ_(CQI). Two reporting configurationsare illustrated in FIGS. 2A and 2B wherein the CQI reporting intervalρ_(CQI)=2 (sub-frames) and M=4. FIGS. 2A and 2B correspond to RI offsetsof ν_(RI)=0 and 1, respectively. It may be noted that the set ofpossible values for ν_(RI) depends on the maximum reporting interval forCQI/PMI, which may be denoted as ρ_(CQI,MAX). The set of values for Mand ν_(RI) is signaled as a part of dedicated system information (e.g.,via RRC signaling), as discussed above. With continued reference toFIGS. 1A, 1B, 2A and 2B, several embodiments of reporting structures arepresented below.

In a first embodiment, the reporting interval and offset values of thecorresponding rank and channel quality indicators may be selectedindependently. That is, the integer multiple M and the RI reportingoffset ν_(RI) are defined independently. In this case, the number ofvalues for ν_(RI) is simply ρ_(CQI,MAX). Assuming that the set of valuesfor M is N_(M), the combination of M and ν_(RI) (RI reportingconfiguration) can be represented in ceil(log₂(N_(M)ρ_(CQI,MAX))) bits.

This assumes the following set of values.

ρ_(CQI)ε{ρ_(CQI,1),ρ_(CQI,2), . . . ,ρ_(CQI,N) _(CQI) }

Mε{M ₁ ,M ₂ , . . . ,M _(N) _(M) }

ν_(RI)ε{0,1,2, . . . ,ρ_(CQI,MAX)−1}

ρ_(CQI,MAX)=max{ρ_(CQI,1),ρ_(CQI,2), . . . ,ρ_(CQI,N) _(CQI) }  (1)

Note that one of the possible values for ρ_(CQI) or M may represent theOFF configuration (where CQI or RI reporting are turned OFF). In thiscase, the above can be modified as follows:

ρ_(CQI)ε{ρ_(CQI,1),ρ_(CQI,2), . . . ,ρ_(CQI,N) _(CQI) ⁻¹,OFF}

Mε{M ₁ ,M ₂ , . . . ,M _(N) _(M) ⁻¹,OFF}

ν_(RI)ε{0,1,2, . . . ,ρ_(CQI,MAX)−1}

ρ_(CQI,MAX)=max{ρ_(CQI,1),ρ_(CQI,2), . . . ,ρ_(CQI,N) _(CQI) ⁻¹}  (2)

With this configuration, the required number of bits to signal the RIreporting configuration is:

ceil(log₂(N _(M) ×N _(CQI)))  (3)

As an example, assume the following set of values (the unit for ρ_(CQI)is subframe, which is equivalent to milliseconds for E-UTRA):

ρ_(CQI)ε{2,5,10,20,40,OFF}

Mε{1,2,5,10,20,40,OFF}  (4)

Using the sets in (4), the simplistic construction is to choose thepossible values for offset ν_(RI)ε{0, 1, 2, . . . , 39}. This requiresceil(log₂(7×40))=9 bits to signal the RI reporting configuration.

In a second embodiment, the reporting interval and offset values for therank indicator are limited by a maximum reporting interval of the rankindicator. While the above first embodiment is simple, it results in anumber of combinations. Since the CQI-related information may beincluded as part of a handover message, it is beneficial to keep thenumber of combinations relatively small and therefore minimize therequired number of bits for signaling. With this in mind, the secondembodiment may be employed to reduce the number of combinations, asdiscussed immediately below.

A maximum RI reporting interval ρ_(RI,MAX) is set. This maximumreporting interval is used to exclude the configurations which result inRI reporting intervals larger than ρ_(RI,MAX). Therefore, fulfilling thefollowing condition is required for a given ρ_(CQI) value.

$\begin{matrix}{M \leq {\frac{\rho_{{RI},{MAX}}}{\rho_{CQI}}.}} & (5)\end{matrix}$

The possible values of M and ν_(RI) are made dependent on each possiblevalue of ρ_(CQI).

Starting from the set of ρ_(CQI) values in (2) (the same can be doneassuming (1)), the following configuration of Table 1 is obtained. Forsimplicity, assume ρ_(CQI,n)<ρ_(CQI,n+1) and M_(n)<M_(n+1).

TABLE 1 ρ_(CQI) Set of values for M Set of values for v_(RI) ρ_(CQI,1)$\{ {M_{1},\ldots \mspace{14mu},M_{n{(1)}}, {OFF} \middle| {M_{n{(1)}} \leq \frac{\rho_{{RI},{MAX}}}{\rho_{{CQI},1}}} } \}${0, 1, . . . , ρ_(CQI,1) − 1} ρ_(CQI,2)$\{ {M_{1},\ldots \mspace{14mu},M_{n{(2)}}, {OFF} \middle| {M_{n{(2)}} \leq \frac{\rho_{{RI},{MAX}}}{\rho_{{CQI},2}}} } \}${0, 1, . . . , ρ_(CQI,2) − 1} . . . ρ_(CQI,N) _(CQI) ⁻¹$\{ {M_{1},\ldots \mspace{14mu},M_{n{({N_{CQI} - 1})}}, {OFF} \middle| {M_{n{({N_{CQI} - 1})}} \leq \frac{\rho_{{RI},{MAX}}}{\rho_{{CQI},{N_{CQI} - 1}}}} } \}${0, 1, . . . , ρ_(CQI,N) _(CQI) ⁻¹ − 1} OFF {OFF} {0}With this configuration, the required number of bits to signal the RIreporting configuration is obtained in (6) below.

ceil(log₂(max{M _(n(m))×ρ_(CQI,m) ,m=1,2, . . . ,N _(CQI)−1}))  (6)

Using the same setup as an example, for the more economical construction(the second example above) with ρ_(RI,MAX)=100, the followingconfiguration of Table 2 is obtained.

TABLE 2 No. possible Set of values Set of values values for a ρ_(CQI)for M for ν_(RI) given ρ_(CQI) 2 {1, 2, 5, 10, 20, 40, OFF} {0, 1}  7 ×2 = 14 5 {1, 2, 5, 10, 20, OFF} {0, 1, 2, 3, 4}  6 × 5 = 30 10 {1, 2, 5,10, OFF} {0, 1, 2, 3, . . . , 8, 9} 5 × 10 = 50 20 {1, 2, 5, OFF} {0, 1,2, 3, . . . , 18, 19} 4 × 20 = 80 40 {1, 2, OFF} {0, 1, 2, 3, . . . ,38, 39}  3 × 40 = 120 OFF {OFF} {0} 1This requires ceil(log₂(120))=7 bits to signal the RI reportingconfiguration.

In a third embodiment, the offset values of the corresponding rank andchannel quality indicators are selected jointly from a same set ofoffset values. That is, it is also possible to jointly define (and henceencode) the CQI/PMI and RI configurations. This is motivated by the factthat the set of possible offset values is the same for CQI/PMI and RIreporting. Note that the offset value for CQI/PMI reporting is definedin the absolute sense while the offset for RI reporting can be definedrelative to the offset for CQI/PMI reporting (although an absoluteoffset definition is not precluded).

That is, the set of possible offset values for RI reporting solelydepends on the periodicity of CQI/PMI reporting. The multiplicativefactor M is then defined separately. The joint definition is describedas follows in Table 3.

TABLE 3 Set of values for ν_(CQI) (CQI/PMI Set of values for ν_(RI)ρ_(CQI) reporting). (RI reporting) ρ_(CQI, 1) {0, 1, . . . , ρ_(CQI, 1)− 1} {0, 1, . . . , ρ_(CQI, 1) − 1} ρ_(CQI, 2) {0, 1, . . . , ρ_(CQI, 2)− 1} {0, 1, . . . , ρ_(CQI, 2) − 1} . . . ρ_(CQI, N) _(CQI) ⁻¹ {0, 1, .. . , ρ_(CQI, N) _(CQI) ⁻¹ − 1} {0, 1, . . . , ρ_(CQI, N) _(CQI) ⁻¹ − 1}OFF {0} {0}With this configuration, the required number of bits to signal theCQI/PMI and RI reporting configuration is

$\begin{matrix}{{{ceil}( {\log_{2}( {N_{M} \times ( {1 + {\sum\limits_{n = 1}^{N_{CQI}}\; n^{2}}} )} )} )}.} & (7)\end{matrix}$

Using the same setup as an example, the following configuration isobtained in Table 4.

TABLE 4 Set of values for ν_(CQI) Set of values No. possible (CQI/PMIfor ν_(RI) (RI values for a ρ_(CQI) reporting) reporting) given ρ_(CQI)2 {0, 1} {0, 1} 2² = 4  5 {0, 1, 2, 3, 4} {0, 1, 2, 3, 4} 5² = 25 10 {0,1, 2, 3, . . . , 8, 9} {0, 1, 2, 3, . . . , 8, 9} 10² = 100 20 {0, 1, 2,3, . . . , 18, 19} {0, 1, 2, 3, . . . , 18, 19} 20² = 400 40 {0, 1, 2,3, . . . , 38, 39} {0, 1, 2, 3, . . . , 38, 39}  40² = 1600 OFF {0} {0}1Combined with M (7 possibilities), this results in a total ofceil(log₂(2131×7))=14 bits, which is 7 extra bits for the RIconfiguration relative to the 7 bits needed(ceil(log₂(2+5+10+20+40+1))=7) only for CQI/PMI configuration. Thisresults in the same saving compared to the second embodiment above.

In a fourth embodiment, which is a combination of the second and thirdembodiments, the reporting interval for the rank indicator is limited bya maximum reporting interval and the offset values of the correspondingrank and channel quality indicators are concurrently selected jointlyfrom a same set of offset values.

In addition to the dependency of ν_(RI) on ρ_(CQI), the set of possiblevalues of M is also made dependent on ρ_(CQI) by setting a maximum RIreporting interval ρ_(RI,MAX) as described in the second embodiment.This combination can be described as follows in Table 5 below.

TABLE 5 ρ_(CQI) Set of values for M Set of values for v_(CQI) Set ofvalues for v_(RI) ρ_(CQI,1)$\{ {M_{1},\ldots \mspace{14mu},M_{n{(1)}}, {OFF} \middle| {M_{n{(1)}} \leq \frac{\rho_{{RI},{MAX}}}{\rho_{{CQI},1}}} } \}${0, 1, . . . , ρ_(CQI,1) − 1} {0, 1, . . . , ρ_(CQI,1) − 1} ρ_(CQI,2)$\{ {M_{1},\ldots \mspace{14mu},M_{n{(2)}}, {OFF} \middle| {M_{n{(2)}} \leq \frac{\rho_{{RI},{MAX}}}{\rho_{{CQI},2}}} } \}${0, 1, . . . , ρ_(CQI,2) − 1} {0, 1, . . . , ρ_(CQI,2) − 1} . . .ρ_(CQI,N) _(CQI) ⁻¹$\{ {M_{1},\ldots \mspace{14mu},M_{n{({N_{CQI} - 1})}}, {OFF} \middle| {M_{n{({N_{CQI} - 1})}} \leq \frac{\rho_{{RI},{MAX}}}{\rho_{{CQI},{N_{CQI} - 1}}}} } \}${0, 1, . . . , ρ_(CQI,N) _(CQI) ⁻¹ − 1} {0, 1, . . . , ρ_(CQI,N) _(CQI)⁻¹ − 1} OFF {OFF} {0} {0}With this configuration, the required number of bits to signal theCQI/PMT and RI reporting configuration is:

$\begin{matrix}{{ceil}( {\log_{2}( {1 + {\sum\limits_{n = 1}^{N_{CQI}}\; {M_{n{(m)}} \times n^{2}}}} )} )} & (8)\end{matrix}$

Using the same setup as an example, the following configuration of Table6 is obtained.

TABLE 6 No. Set of Set of possible values for values for values forν_(CQI) (CQI/PMI ν_(RI) (RI Set of values a given ρ_(CQI) reporting)reporting) for M ρ_(CQI) 2 {0, 1} {0, 1} (1, 2, 5, 10, 20, 40, OFF} 7 ×2² = 28  5 {0, 1, 2, 3, 4} {0, 1, 2, 3, 4} {1, 2, 5, 10, 20, OFF} 6 × 5²= 150 10 {0, 1, 2, 3, . . . , 8, 9} {0, 1, 2, 3, . . . , 8, 9} {1, 2, 5,10, OFF} 5 × 10² = 500  20 {0, 1, 2, 3, . . . , 18, 19} {0, 1, 2, 3, . .. , 18, 19} {1, 2, 5, OFF} 4 × 20² = 1600 40 {0, 1, 2, 3, . . . , 38,39} {0, 1, 2, 3, . . . , 38, 39} {1, 2, OFF} 3 × 40² = 4800 OFF {0} {0}{OFF} 1This result provides a total of ceil(log₂(28+150+500+1600+4800+1))=13bits, which is 6 extra bits for the RI configuration relative to the 7bits needed (ceil(log₂(2+5+10+20+40+1))=7) only for the CQI/PMIconfiguration.

It may be noted that modifications to the above embodiments are includedin this disclosure as long as they maintain the structure. For instance,it is possible to exclude an OFF configuration for ρ_(CQI) or M asindicated in (1). Furthermore, it is possible to further restrict thepossible offset values ν as a subset of {0, 1, 2, . . . , ρ_(CQI,n)−1}.That is, not all possible offset values from zero to ρ_(CQI,n)−1 areused. Other extensions and variations are also possible. The aboveembodiments may be combined with other schemes to further restrict thenumber of configurations.

Regarding the definition of the offset values, it is important to definean absolute reference which can be used for defining the CQI/PMIreporting offset ν_(CQI). In addition, it may also be used to define theRI reporting offset ν_(RI) if it is defined as an absolute offset(instead of a relative offset). Since the CQI/PMI reporting periodicity(interval) ρ_(CQI)(ms) may be a multiple of a radio frame duration, theabsolute reference cannot be defined within a 10 ms radio frame.Additionally, the offset value is a multiple of one subframe duration (1ms).

Hence, the reference and the offset definition may be defined as afunction of the subframe number within the CQI/PMI reporting periodicity(interval) ρ_(CQI). Alternatively, the maximum CQI/PMI reportingperiodicity can also be used. The subframe number can be enumeratedbased on the system frame number (SFN, which starts at zero) and thenumber of subframes per radio frame (equals ten in E-UTRA).

For instance, the first subframe (subframe zero) within the ρ_(CQI) timeframe is used as the absolute offset reference. The CQI/PMI reportingoffset ν_(CQI) is defined relative to the absolute reference. Hence, theoffset can be written as follows.

$\begin{matrix}{{v_{CQI} = {( {{{SFN} \times 10} + n} ){{mod}( \frac{\rho_{CQI}}{T_{subframe}} )}}},{or}} & (9) \\{v_{CQI} = {{( {{SFN}\; {{mod}( \lceil \frac{\rho_{CQI}}{T_{frame}} \rceil )}} ) \times 10} + {n.}}} & (10)\end{matrix}$

Here, T_(subframe)=1 ms and T_(frame)=10 ms f for E-UTRA and n is theoffset index (0, 1, 2, . . . , 9) within one radio frame (following thefact that there are 10 subframes within one radio frame). Essentially,this defines the valid locations (in terms of subframes) of the CQI/PMIreports for a given CQI/PMI reporting offset parameter ν_(CQI), whichmay be configured by the network via a higher layer or broadcastsignaling.

A simplification may be obtained by expressing the CQI/PMI reportingperiodicity in terms of subframes. In this case, the above formula canbe simplified as ν_(CQI)=(SFN×10+n)mod P_(CQI). where P_(CQI) is theCQI/PMI reporting intervals defined in subframes. For example, itρ_(CQI)=40 ms (multiple of 10 ms), the above equations become

ν_(CQI)=(SFN×10+n)mod 40, or  (11)

ν_(CQI)=(SFN mod 4)×10+n.  (12)

Therefore, if a CQI/PMI reporting is assigned an offset corresponding tothe offset index of five (where indexing starts at zero) starting inradio frame with SFN=35, the resulting ν_(CQI) is 35. For example, ifρ_(CQI)=5 ms(

10 ms), the above equations become

ν_(CQI)=(SFN×10+n)mod 5, or  (13)

ν_(CQI) =n.  (14)

As mentioned, it is also possible to define a reference using themaximum/worst-case CQI/PMI reporting periodicity/interval ρ_(CQI,MAX)regardless of ρ_(CQI). In this case, the equations become

$\begin{matrix}{{v_{CQI} = {( {{{SFN} \times 10} + n} ){{mod}( \frac{\rho_{{CQI},{MAX}}}{T_{subframe}} )}}},{or}} & (15) \\{v_{CQI} = {{( {{SFN}\; {{mod}( \lceil \frac{\rho_{{CQI},{MAX}}}{T_{frame}} \rceil )}} ) \times 10} + {n.}}} & (16)\end{matrix}$

For instance, if ρ_(CQI,MAX)=160 ms, the above equations become

ν_(CQI)=(SFN×10+n)mod 160, or  (17)

ν_(CQI)=(SFN mod 16)×10+n.  (18)

The equations will be used regardless of the reporting periodicityρ_(CQI).

While the above embodiments are described for CQI/PMI reporting, theprinciples may also be applied to other periodic transmissions. Oneexample is the transmission of an uplink sounding reference signal,which shares similar structures as that for CQI/PMI reporting. Inparticular, the same offset definition can be used whereν_(SRS)=(SFN×10+n)mod P_(SRS). Here, P_(SRS) is the SRS reportingperiodicity and n is the offset index (0, 1, 2, . . . , 9) within oneradio frame. This defines the valid location (in terms of subframes) forSRS reporting given the offset parameter ν_(SRS), which is configured bythe network via higher layer or broadcast signaling.

FIG. 3 illustrates a flow diagram of an embodiment of a method ofoperating a reporting allocation unit, generally designated 300, carriedout according to the principles of the present disclosure. The method300 is for use in a base station and starts in a step 305. Then, in astep 310, the base station is provided and reporting interval and offsetvalues of corresponding rank and channel quality indicators for userequipment are provided in a step 315. The reporting interval and offsetvalues are transmitted to the user equipment in a step 320.

In one embodiment, the reporting interval and offset values of thecorresponding rank and channel quality indicators are selectedindependently. In another embodiment, the reporting interval and offsetvalues for the rank indicator are limited by a maximum reportinginterval of the rank indicator. In yet another embodiment, the offsetvalues of the corresponding rank and channel quality indicators areselected jointly from a same set of offset values. In still anotherembodiment, the reporting interval for the rank indicator is limited bya maximum reporting interval of the rank indicator and the offset valuesof the corresponding rank and channel quality indicators areconcurrently selected jointly from a same set of offset values. In afurther embodiment, the offset values are derived as a function of asystem frame number parameter. The method 300 ends in a step 325.

FIG. 4 illustrates a flow diagram of an embodiment of a method ofoperating an indicator reception unit, generally designated 400, carriedout according to the principles of the present disclosure. The method400 is for use in user equipment and starts in a step 405. Then, in astep 410, the user equipment is provided and reporting interval andoffset values for corresponding rank and channel quality indicators arereceived from a base station in a step 415. The reporting interval andoffset values are provided for feeding back the corresponding rank andchannel quality indicators to the base station in a step 420.

In one embodiment, the reporting interval and offset values of thecorresponding rank and channel quality indicators are selectedindependently. In another embodiment, the reporting interval and offsetvalues for the rank indicator are limited by a maximum reportinginterval of the rank indicator. In yet another embodiment, the offsetvalues of the corresponding rank and channel quality indicators areselected jointly from a same set of offset values. In still anotherembodiment, the reporting interval for the rank indicator is limited bya maximum reporting interval of the rank indicator and the offset valuesof the corresponding rank and channel quality indicators areconcurrently selected jointly from a same set of offset values. In afurther embodiment, the offset values are derived as a function of asystem frame number parameter. The method 400 ends in a step 425.

While the methods disclosed herein have been described and shown withreference to particular steps performed in a particular order, it willbe understood that these steps may be combined, subdivided, or reorderedto form an equivalent method without departing from the teachings of thepresent disclosure. Accordingly, unless specifically indicated herein,the order or the grouping of the steps is not a limitation of thepresent disclosure.

Those skilled in the art to which the disclosure relates will appreciatethat other and further additions, deletions, substitutions andmodifications may be made to the described example embodiments withoutdeparting from the disclosure.

1. A reporting allocation unit, comprising: an indicator configurationmodule configured to provide reporting interval and offset values ofcorresponding rank and channel quality indicators for user equipment;and a sending module configured to transmit the reporting interval andoffset values to the user equipment.
 2. The reporting allocation unit asrecited in claim 1 wherein the reporting interval and offset values ofthe corresponding rank and channel quality indicators are selectedindependently.
 3. The reporting allocation unit as recited in claim 1wherein the reporting interval and offset values for the rank indicatorare limited by a maximum reporting interval of the rank indicator. 4-6.(canceled)
 7. A method of operating a reporting allocation unit,comprising: providing reporting interval and offset values ofcorresponding rank and channel quality indicators for user equipment;and transmitting the reporting interval and offset values to the userequipment.
 8. The method as recited in claim 7 wherein the reportinginterval and offset values of the corresponding rank and channel qualityindicators are selected independently.
 9. The method as recited in claim7 wherein the reporting interval and offset values for the rankindicator are limited by a maximum reporting interval of the rankindicator. 10-12. (canceled)
 13. An indicator interpretation unit,comprising: a receive module configured to receive reporting intervaland offset values for corresponding rank and channel quality indicatorsfrom a base station; and a reporting configuration module configured toprovide the reporting interval and offset values for feeding back thecorresponding rank and channel quality indicators to the base station.14. The indicator interpretation unit as recited in claim 13 wherein thereporting interval and offset values of the corresponding rank andchannel quality indicators are selected independently.
 15. The indicatorinterpretation unit as recited in claim 13 wherein the reportinginterval and offset values for the rank indicator are limited by amaximum reporting interval of the rank indicator. 16-18. (canceled) 19.A method of operating an indicator interpretation unit, comprising:receiving reporting interval and offset values for corresponding rankand channel quality indicators from a base station; and providing thereporting interval and offset values for feeding back the correspondingrank and channel quality indicators to the base station.
 20. The methodas recited in claim 19 wherein the reporting interval and offset valuesof the corresponding rank and channel quality indicators are selectedindependently.
 21. The method as recited in claim 19 wherein thereporting interval and offset values for the rank indicator are limitedby a maximum reporting interval of the rank indicator. 22-24. (canceled)